In a wideband wireless communication system, an idle mode is supported to reduce power consumption of a mobile terminal. The idle mode starts by any one of a terminal or a serving base station to which the terminal belongs.
Hereinafter, messages used for a terminal to transition to an idle mode will be described in detail.
AAI DREG-REQ and AAI DREG-RSP Message
Table 1 shows deregistration codes of deregistration request (AAI_DREG-REQ) messages and descriptions of respective deregistration request codes.
TABLE 1Attributes/Array ofM/OattributesSize(bits)Value/NoteConditionsMDe-3Used to indicate the purpose of this messageN.A.registration_Request_Code0x00: AMS deregistration request from ABS andnetwork0x01: request for AMS deregistration from servingABS and initiation of AMS idle mode.0x02: response for the unsolicited AAI_DREG-RSP message with action code 0x05 by the ABS.0x03: reject for the unsolicited AAI_DREG-RSPmessage with action code 0x05 by the ABS. Thiscode is applicable only when an AMS has a pendingUL data to transmit.0x04: request for AMS deregistration from servingABS to enter DCR mode0x05: response for the unsolicited AAI_DREG-RSP message with action code 0x00, 0x01, 0x02or 0x030x06-0x07: reserved
With reference to Table 1, a terminal sets a deregistration request code De-registration_Request_Code) of a deregistration request message to ‘01’ and transmits the same to a base station to request that the terminal will transition to an idle mode. Also, when the terminal receives an unsolicited registration response message including an operation code ‘05’ instructing the terminal to transmit a deregistration request message for a transition to an idle mode from the BS, the terminal sets the deregistration request code (De-registration_Request_Code) to ‘02’ of the deregistration request message and transmits the same to the base station in response thereto.
Table 2 below shows action codes of a deregistration response (AAI_DREG-RSP) and descriptions of operations of a terminal instructed by respective action codes.
TABLE 2Attributes/Array ofM/OattributesSize (bits)Value/NoteConditionsMAction code4Used to indicate the purpose of this messageN.A.0x00: AMS shall immediately terminate servicewith the ABS and should attempt network entryat another ABS0x01: AMS shall listen to the current ABS butshall not transmit until a RES-CMD message orAAI_DREG-RSP message with action code 0x02or 0x03 is received.0x02: AMS shall listen to the current ABS butonly transmit on the control connection.0x03: AMS shall return to normal operation andmay transmit on any of its active connections.0x04: This option is valid in response to aAAI_DREG-REQ message with De-RegistrationRequest Code = 0x00. The AMS shall terminatecurrent Normal Operation with the ABS.0x05: AMS shall begin idle mode initiation: a) tosignal AMS to begin idle mode in unsolicitedmanner or b) to allow AMS to transmit AMS-initiatedidle mode request at the REQ-Durationexpiration0x06: This option is valid only in response to aAAI_DREG-REQ message with De-RegistrationCode 0x01: a) to reject AMS-initiated idle moderequest or b) to allow AMS to transmit AMS-initiatedidle mode request at the REQ-Durationexpiration0x07: This option is valid in response to aAAI_DREG-REQ message with De-registration-request-code = 0x01 to allow AMS-initiated idlemode request.0x08: This option is valid only in response to anAAI_DREG-REQ message with De-RegistrationRequest Code 0x04 to allow retention of theAMS's connection information0x09: This option is valid only in response to anAAI_DREG-REQ message with De-RegistrationRequest Code 0x04 to reject retention of theAMS's connection information.0x10-0x15: reserved
With reference to Table 2, when the base sets the action code to ‘05’ and transmits a deregistration response message to the terminal, the terminal starts a transition to an idle mode in an unsolicited manner or transmits a deregistration request message for requesting a transition to an idle mode after the expiry of REQ-Duration. Namely, the action code ‘05’ is a code instructing the terminal to start to transition to an idle mode.
Also, when the base station receives a deregistration request message including a deregistration request code ‘01’ from the terminal, the base station sets an action code ‘07’ and transmits a deregistration response message to the terminal in response thereto.
MCEH (MAC Control Extended Header), MAEH (MAC Control Message ACK Extended Header) and AAI MSG-ACK Message
Table 3 below shows an example of a format of an MCEH (MAC Control Extended Header).
TABLE 3SizeSyntax(bit)NotesMCEH ( ) { Type4Extended header type = 0b0010(MCEH Type) Control Connection Channel1Channel ID to identify separate ID (CCC ID)fragmentation/reassemblystate machines0: channel 11: channel 2  Polling10 = no acknowledgementrequired1 = acknowledge required uponreceiving the MAC message  FC2Fragmentation control(see Table 669)  SN8Payload sequence number, SNis maintained per CCC ID, the‘SN’ value increments by one(modulo 256) sequentially.}
With reference to Table 3, the MCEH includes a polling parameter indicating a response with respect to whether or not a message has been received. For example, when a poll bit is set to ‘1’, it requests a response with respect to a message reception, and when the poll bit is set to ‘0’, it does not request a response with respect to a message reception.
Table 4 below shows an example of a format of an MAEH (MAC Control message ACK Extended Header).
TABLE 4SyntaxSize (bits)NotesMAEH ( ) {Type4Extended header type =0b0100 (MAEH type)MAEH sub-type10b0: Indicates reception of acontrol message0b1: Indicates reception of aService SpecificScheduling Control headerIf (MAEH sub-type == 0b0) {ACK_SN6SN retrieved from the MCEHof the MAC PDU with thePolling bit set to 1Control Connection1Control Connection ChannelChannel ID (CCC ID)ID (CCC ID) that the MACcontrol message is received.}ReservedVariableFor byte alignment}
The MAEH may be used by a terminal or a base station in order to instruct a response with respect to a received MAC control message. When the base station or the terminal receives a MAC control message in which a poll bit of the MCEH is set to ‘1’, or a portion of the MAC control message, the base station or the terminal transmits the MAEH as an acknowledgement thereto.
Table 5 below shows an example of an AAI_MSG-ACK message format.
TABLE 5Attributes/Array ofSizeM/Oattributes(bits)Value/NoteConditionsMACK_SN6SN retrieved from MCEHN.A.of the received MAC PDU.MCCC ID1Control Connection Channel IDN.A.(CCC ID) that the MACmanagement message is received.
The base station or the terminal may use an AAI_MSG-ACK message in order to indicate a reception of a MAC management. When the base station or the terminal receives a MAC message including the MCEH in which a poll bit is set to ‘1’, the base station or the terminal transmits an AAI_MSG-ACK message as an acknowledgement thereto.
AMS Initiated Idle Mode Entry
FIG. 1 is a flow chart illustrating a process of transitioning to an idle mode started by a terminal according to the related art.
With reference to FIG. 1, when the terminal wants to transition to an idle mode, the terminal transmits a deregistration request (DREG-REQ) message including a deregistration request code ‘01’ to the base station (step S11). The base station a deregistration (DREG-RSP) message including an action code ‘07’ in response to the DREG-REQ message which has been transmitted from the terminal (step S12). Upon receiving the DREG-RSP message, the terminal transitions to an idle mode (step S13).
Type 1 ABS Initiated Idle Mode Entry
FIG. 2 is a flow chart illustrating a process of transitioning to an idle mode by Type 1 ABS initiation according to the related art.
With reference to FIG. 2, in order to instruct the terminal to transition to an AMS initiated idle mode, the base station transmits a DREG-RSP message including an action code ‘05’ to the terminal (step S21). Upon receiving the DREG-RSP message, the terminal transmits a DREG-REQ (including deregistration request code ‘02’) in which a poll bit in the MCEH (MAC Control Extended Header) is set to ‘1’ to the base station in response thereto (step S22). Upon receiving the DREG-REQ message, the base station transmits an AAI_MSG-ACK message to the terminal (step S23).
Type 2 ABS Initiated Idle Mode Entry
FIG. 3 is a flow chart illustrating a process of transitioning to an idle mode by Type 2 ABS initiation according to the related art.
With reference to FIG. 3, the base station transmits a DREG-RSP message including an action code ‘05’ along with an REQ-Duration to the terminal in order to instruct the terminal to transition to an AMS initiated idle mode (step S31). Upon receiving the DREG-RSP message, the terminal transmits a DREG-REQ message including a deregistration request code ‘01’ to the base station before an REQ-Duration timer expires in response thereto (step S32). Upon receiving the DREG-REQ message, the base station transmits a DREG-RSP message including an action code ‘05’ allowing the terminal to transition to an idle mode, to the terminal (step S33).
FIG. 4 is a flow chart illustrating a situation in which the DREG-RSP message is lost during the process of transitioning to an idle mode by Type 2 ABS initiation according to the related art.
During the Type 2 ABS initiated idle mode entry process, the base station transmits a DREG-RSP message including the action code ‘05’ instructing the terminal to transition to the AMS initiated idle mode, to the terminal. Here, it may happen that the DREG-RSP message is lost while being transmitted and the terminal transmits the DREG-REQ message including the deregistration request code ‘01’ requesting a transition to an idle mode to the base station (step S42).
In this case, the base station may consider an AAI_DREG-REQ (including the deregistration request code ‘01’) message received from the terminal as a response to an unsolicited AAI_DREG-RSP (including the action code ‘05’) the base station has transmitted to the terminal, and transmits an AAI_DREG-RSP (including the action code ‘05’) to the terminal in response thereto (step S43).
However, the terminal has not received the AAI_DREG-RSP (including the action code ‘05’) the base station had transmitted, the terminal expects to receive an AAI_DREG-RSP (including an action code ‘07’) from the base station (step S44). In this case, there is delay during the process of transitioning to an idle mode of the terminal.